using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;

using Org.BouncyCastle.Math;

namespace Org.BouncyCastle.Asn1
{
    public class DerObjectIdentifier
        : Asn1Object
    {
        private static readonly Regex OidRegex = new Regex(@"\A[0-2](\.[0-9]+)+\z");

        private readonly string identifier;

        /// <summary>
        /// Return OID from argument
        /// </summary>
        /// <param name="obj">a DerObjectIdentifier down-cast to Object, or null</param>
        /// <returns>obj as DerObjectIdentifier</returns>
        /// <exception cref="ArgumentException">obj is not null or a DerObjectIdentifier instance</exception>
        public static DerObjectIdentifier GetInstance(
            object obj)
        {
            if (obj == null || obj is DerObjectIdentifier)
            {
                return (DerObjectIdentifier) obj;
            }

            throw new ArgumentException("illegal object in GetInstance: " + obj.GetType().Name, "obj");
        }

        /// <summary>
        /// Return DerObjectIdentifier from a tagged object
        /// </summary>
        /// <param name="obj">tagged object holding DerObjectIdentifier</param>
        /// <param name="explicitly">obj is meant to be explicitly tagged</param>
        /// <returns>DerObjectIdentifier contained by tagged object</returns>
        /// <exception cref="ArgumentException">The tagged object cannot be converted</exception>
        public static DerObjectIdentifier GetInstance(
            Asn1TaggedObject	obj,
            bool				explicitly)
        {
            return GetInstance(obj.GetObject());
        }

        /// <summary>
        /// Return DerObjectIdentifier from string representation of OID
        /// </summary>
        /// <param name="identifier">String representation of an object Identifier (not null)</param>
        /// <exception cref="ArgumentNullException">identifier is null</exception>
        /// <exception cref="FormatException">identifier is not an OID</exception>
        public DerObjectIdentifier(
            string identifier)
        {
            if (identifier == null)
                throw new ArgumentNullException("identifier");
            if (!OidRegex.IsMatch(identifier))
                throw new FormatException("string " + identifier + " not an OID");

            this.identifier = identifier;
        }

        /// <summary>
        /// Return DerObjectIdentifier from int array
        /// </summary>
        /// <param name="identifier">int array of OID components</param>
        /// <remarks>Useful for interoperability with obj-sys.com ASN.1 code generator</remarks>
        public DerObjectIdentifier(
            int[] identifier) 
        {
            StringBuilder s = new StringBuilder();
            foreach (int i in identifier)
            {
                s.Append(i.ToString() + ".");
            }
            // get rid of trailing "."
            s.Remove(s.Length - 1, 1);
            this.identifier = s.ToString();
        }

        /// <summary>
        /// Return int[] of OID components
        /// </summary>
        /// <returns>int[] of OID components in order</returns>
        /// <remarks>Useful for interoperability with obj-sys.com ASN.1 code generator</remarks>
        public int[] AsIntArray()
        {
            string[] mc = identifier.Split(new char[] { '.' });
            int[] ia = new int[mc.Length];
            for (int i = 0; i < mc.Length; i++)
            {
                ia[i] = Convert.ToInt32(mc[i]);
            }
            return ia;
        }

        public string Id { get { return identifier; } }

        /// <summary>
        /// Returns a new DerObjectIdentifier from this OID's child space
        /// </summary>
        /// <param name="branchID">string representing which child to reference</param>
        /// <returns>new DerObjectIdentifier of this.identifier.Append(branchID)</returns>
        public virtual DerObjectIdentifier Branch(string branchID)
        {
            return new DerObjectIdentifier(identifier + "." + branchID);
        }

        /// <summary>
        /// Create a new DerObjectIdentifier from a byte array
        /// </summary>
        /// <param name="bytes">bytes from which to create the DerObjectIdentifier</param>
        internal DerObjectIdentifier(
            byte[] bytes)
            : this(MakeOidStringFromBytes(bytes))
        {
        }

        private void WriteField(
            Stream	outputStream,
            long	fieldValue)
        {
            byte[] result = new byte[9];
            int pos = 8;
            result[pos] = (byte)(fieldValue & 0x7f);
            while (fieldValue >= (1L << 7))
            {
                fieldValue >>= 7;
                result[--pos] = (byte)((fieldValue & 0x7f) | 0x80);
            }
            outputStream.Write(result, pos, 9 - pos);
        }

        private void WriteField(
            Stream		outputStream,
            BigInteger	fieldValue)
        {
            int byteCount = (fieldValue.BitLength + 6) / 7;
            if (byteCount == 0)
            {
                outputStream.WriteByte(0);
            }
            else
            {
                BigInteger tmpValue = fieldValue;
                byte[] tmp = new byte[byteCount];
                for (int i = byteCount-1; i >= 0; i--)
                {
                    tmp[i] = (byte) ((tmpValue.IntValue & 0x7f) | 0x80);
                    tmpValue = tmpValue.ShiftRight(7);
                }
                tmp[byteCount-1] &= 0x7f;
                outputStream.Write(tmp, 0, tmp.Length);
            }
        }

        internal override void Encode(
            DerOutputStream derOut)
        {
            OidTokenizer tok = new OidTokenizer(identifier);
            MemoryStream bOut = new MemoryStream();
            DerOutputStream dOut = new DerOutputStream(bOut);

            string token = tok.NextToken();
            int first = int.Parse(token);

            token = tok.NextToken();
            int second = int.Parse(token);

            WriteField(bOut, first * 40 + second);

            while (tok.HasMoreTokens)
            {
                token = tok.NextToken();
                if (token.Length < 18)
                {
                    WriteField(bOut, Int64.Parse(token));
                }
                else
                {
                    WriteField(bOut, new BigInteger(token));
                }
            }

            dOut.Close();

            derOut.WriteEncoded(Asn1Tags.ObjectIdentifier, bOut.ToArray());
        }

        /// <summary>
        /// Returns a HashCode referring to this
        /// </summary>
        /// <returns>HashCode for the string value of this's OID</returns>
        protected override int Asn1GetHashCode()
        {
            return identifier.GetHashCode();
        }

        protected override bool Asn1Equals(
            Asn1Object asn1Object)
        {
            DerObjectIdentifier other = asn1Object as DerObjectIdentifier;

            if (other == null)
                return false;

            return this.identifier.Equals(other.identifier);
        }

        /// <summary>
        /// Convert this DerObjectIdentifier to its string representation
        /// </summary>
        /// <returns>this DerObjectIdentifier's string representation</returns>
        public override string ToString()
        {
            return identifier;
        }

        private static string MakeOidStringFromBytes(
            byte[] bytes)
        {
            StringBuilder	objId = new StringBuilder();
            long			value = 0;
            BigInteger		bigValue = null;
            bool			first = true;

            for (int i = 0; i != bytes.Length; i++)
            {
                int b = bytes[i];

                if (value < 0x80000000000000L)
                {
                    value = value * 128 + (b & 0x7f);
                    if ((b & 0x80) == 0)             // end of number reached
                    {
                        if (first)
                        {
                            switch ((int)value / 40)
                            {
                                case 0:
                                    objId.Append('0');
                                    break;
                                case 1:
                                    objId.Append('1');
                                    value -= 40;
                                    break;
                                default:
                                    objId.Append('2');
                                    value -= 80;
                                    break;
                            }
                            first = false;
                        }

                        objId.Append('.');
                        objId.Append(value);
                        value = 0;
                    }
                }
                else
                {
                    if (bigValue == null)
                    {
                        bigValue = BigInteger.ValueOf(value);
                    }
                    bigValue = bigValue.ShiftLeft(7);
                    bigValue = bigValue.Or(BigInteger.ValueOf(b & 0x7f));
                    if ((b & 0x80) == 0)
                    {
                        objId.Append('.');
                        objId.Append(bigValue);
                        bigValue = null;
                        value = 0;
                    }
                }
            }

            return objId.ToString();
        }
    }
}
